Effect of hyperglycemia on blood flow, pH, and response to hyperthermia (42 degrees) of the Yoshida sarcoma in the rat.

Hyperglycemia (blood glucose, > 20 mmol/liter) caused a 90 to 100% inhibition of blood flow in the solid Yoshida sarcoma of rat feet, as measured by the fractional distribution of 86Rb and 133Xe clearance. Blood flow through the normal gastrocnemius muscle was increased by 50%, while liver blood flow remained unaltered. Hyperglycemia abrogated the temperature differential (approximately 1 degree) between the heating bath and the tumor, promoting more uniform tumor heating. During the period of reduced blood flow, the pH of the tumor extracellular fluid, measured by miniature glass electrode, declined from 7.19 to 6.63 due to decreased efflux of lactate from the tumor. Tumor intracellular pH, measured by partitioning of dimethyloxazolidinedione across the cell membrane, increased from 7.21 to 7.36. At a very high blood glucose concentration (50 mmol/liter), the tumor was isolated from the host, with almost total blockade of water, chloride, glucose, lactate, and dimethyloxazolidinedione exchange between the tumor and the blood. Hyperglycemia therefore represents a convenient means of isolating the Yoshida sarcoma from the host blood supply to enable more selective treatment with hyperthermia and possibly other modalities.